N-Alkylimidazoles such as, e.g., 2-alkyl-4-halo-1-(4-halobenzyl)-5-formylimidazoles are useful as raw materials for medicines such as diuretics and hypotensive drugs. In J. Org. Chem., 59, 6391-6394 (1994) is disclosed a method in which 2-n-butyl-4-chloro-5-formylimidazole is reacted with 4-bromobenzyl bromide together with powdery potassium carbonate at -10.degree. C. in N,N-dimethylacetamide to benzylate the imidazole.
However, powdery potassium carbonate has drawbacks in that it is apt to fly off during handling and is highly hygroscopic, although the yield of the target compound in the above method is as high as 93%. Hence, the above method is not always advantageous when practiced on an industrial scale.